By Geraldine Amiel

PARIS--The European Central Bank stands ready to "intervene" again if necessary to preserve the euro's stability, its president Mario Draghi said Friday, in a reference to the "unconventional means" the ECB has pledged to use.

In September, Mr. Draghi announced that the central bank could buy a potentially unlimited quantity of the bonds of struggling euro-zone governments, under strict conditions. Germany's Bundesbank has repeatedly opposed the policy, warning that it is akin to financing governments.

Speaking in a live interview with French radio Europe 1, Mr. Draghi said that the euro zone isn't yet out of the crisis and that the first signs of its economic recovery won't show until the second half of next year. When asked if 2013 could actually prove more positive than expected, Mr Draghi answered "I hope so."

The short-term economic contraction experienced by the euro zone is "unavoidable," as the bloc is addressing its sovereign debt issues, but this should set the base for a sounder economy providing structural reforms are put into place, Mr. Draghi added.

Greece's international creditors reached a deal earlier this week on the terms of its continuing bailout which unlocked about 44 billion euros ($57 billion) in long-delayed loan payments. Asked whether Greece would remain a member of the euro zone, Mr. Draghi said "the answer is positive."

Write to GĂ©raldine Amiel at geraldine.amiel@dowjones.com